Telephone-switchboard lamp



' Nov. 8, 1927.

W. G. LASKEY TELEPHONE SWITCHBOARD LAMP Filed March 27, 1.924

Patented Nov. 8, 927. 1,647,999 UNITED STATES PATENT OFFICE.

WILLIAM G. LASKEY, OF NEW YORK, N. Y., .ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-SWITCHBIOARD LAMP.

Application filed March 27, 1924. Serial No. 702,184.

Other features and objects of the invention will appear from the following descrip tion taken in connection with the attached drawings.

Fig. 1 shows the relative positions of the wire and the internal tube; Fig. 1 shows in more detail the support and leading-in wires; Fig. 2 shows the three parts of the lamp, the filament, outer tube and inner tube in position for heating and the arms for the application of pressure subsequent to the heating; Fig. 3 shows a lamp after the initial heating and pressure; Fig. 4 shows a finished lamp with the evacuating tube sealed off after evacuating the bulb and the addition of the terminals; and Fig. 5 is asection taken along line 55 of Fig. 2 showing the shape of the pressing jaws when in position for exerting pressure against the base of the bulb.

Referring to Fig. 1 a glass tube 3 of uniform cross section is clamped in a device (not shown) together with the filament and lead-in wires 1 whichhave been bent to the form desired. A small globule of glass 2 is added to the sup ort wires to hold them in form and to make them more rigid. The form should be similar to that shown in Fig. 1 the bends and 11 being perpendicular to the longitudinal axis of the glass bead v2 and acting as guides in positioning the support wires. The external bulb 4, Fig. 2, is clamped in another device (not shown) and brought into position relative to the filament and tube 3 which it takes in the finished lamp. In this position, tube 3 projects into the bulb only a suflicient distance to insure a satisfactory weld as hereinafter described.

With the elements of the lamp positioned as shown in Fig. 2, they are caused to rotate at the same speed and while rotating, flames 12 from Bunsen burners orsimilar devices are directed against the lower portion of the bulb where it overlaps tube 3.

When the glass has become somewhat softened .ue to the application of heat, a sli ht blow is struck at the softened portion by jaws 6. This blow or. sudden pressure forces the glass of the external bulb around the tube and wires. During this operation small wings are formed as at 7, Fig. 3. The shape of the jaws 6, shown in Fig. 5, is such as to force the glass of the bulb 4 around the wires 1 and into contact with tube 3. Pro- This invention relates to evacuated bulbs having electrodes contained therein and own generally as incandescent filament electric lamps and more specifically to such 5 lamps as are used for signaling purposes in telephone switchboards or similar devices.

An object of the invention is to produce a small lamp of simple and inexpensive construction, retaining the tipless feature made 10 possible by exhausting the bulb through the central portion of the base.

The signal lamps at present in use, have a stem of peculiar shape for supporting the lead-in wires which in turn support the 15 filament. The peculiar shaped stem is necessary to obtain an air tight seal between the stem and the enclosing bulb. Another considera'tion is brought in by the necessity of having lead-in wires pass through this seal.

To insure an air tight seal having wires passing through it, the wires must be very small so that the glass when softened will flow all around the wire and give the seal required. Wire of material that will not be destroyed in the heat required to make the seal is there fore necessary. Platinum wire is commonly used for lead in wires because it possesses the essential characteristics even when of very small diameter.

A feature of this invention is the elimination of the stem within the bulb and the use of the lead-in wires of comparatively large diameter. These larger wires may be of the kind known commercialy as Dumet and may have a diameter of approximately 10 to 12 mils (.010 inch .012 inch) whereas the platinum wire commonly used has a diameter of approximately 5 mils (.005 inch). Dumet wire also has approximately the same 4 coeflicient of expansion as glass.

Another feature of the invention is the simplicity of construction and the small number of component parts. This simplicity of construction is due primarily to the 4 manner of making the seal between the bulb and the inner tube and the manner of bringing in the leads. This seal is made in two operations and requires a machine of the type well known in the art. Each operation consists of the application of heat and the subsequent application of pressure. The first. operation forms the glass in such a way that the second heating causes the glass to fiow around the leading-in wires thereby insuring an air tight seal of the elements.

- sealed off as at 8.

described in Patent709,996, dated Septem- .jec'tions 13 are formed on the arms to keep them from crushing the molten glass to such an extent as toelose up the tube?) thereby defeating its primary function as an evacu== ating tube.

Heat is again applied in the same manner -as before causing the glass to flow more the Wires and -a second completely about blow is struck with arms 6. This time the blow is struck at right angles to the direction of the first blow and in addition to forcing the glasswinto closer contact all around, it smooths out the wings giving this portion of the assembly a more nearly'umform cylindrical shape.

The air is then removed through tube 3 in the usual manner and the tube hermetically Terminals 9 of the type I. on opposite sides of inserting a glass evacuating tube between the leading-in wires, positioning the bulb said tube extends a short distance into the base of said bulb, applying heat to the exterior of said base suflicient tosoften the glass but insuflicient to fuse said bulb to said tube, mechanically pressing the softened glass into intimate contact with said leadingin wires and said evacuating tube to form an air tight seal.

so that v 2. A method of sealing base/metal leading-in Wires to glass bulbs which consists in inserting a glass evacuating tube be tween the leading-in wires, positioning the.

bulb so that said tube extends a short distance into the base of said heat to the exterior of said base sufiicient to soften the glass but insuflicient to said bulb to said tube, mechanically pressing softened glass into intimate contact with said leading-in wires and said evacuatin tube, again applying heat at said base su ficient to soften the glass, and applying pressure on opposite sides of said base at right angles to said first application of pressure to form an air tight seal between said bulb, evacuating tube and leading-in wires.

In witness whereof, I my name this 24th day of March A. D., 1924.-

. WILLIAM G. LASKEY..

fuse

said base to force the bulb, applying hereunto subscribe 

